The present invention is directed to the art of bandages, wound dressings, or patches useful in modulating the supply of oxygen to skin wounds. The invention is particularly useful in supplying localized and predetermined dosages of concentrated oxygen directly to skin wounds topically without incurring systemic toxic side effects associated with extreme amounts of oxygen, as may occur in connection with hyperbaric oxygen chamber techniques of the prior art.
Hyperbaric oxygen therapy is used for inducing the growth of blood vessels for stimulating growth of new skin tissue to close and heal ischemic wounds. The systemic therapy has its drawbacks, however. For example, hyperbaric oxygen may produce vasoconstriction, toxicity and tissue destruction. When offered systemically, there is a risk of central nervous system and pulmonary toxicity. Topical hyperbaric oxygen therapy, on the other hand, avoids systemic toxicity but is useful for open wounds and has proven effective in healing recalcitrant skin wounds. The toxic effect from excessive topical oxygen can lead to cessation of healing as it can be toxic to endothelial cells surrounding the wound. Devasculation occurs, and neovasculation ceases. Any damage caused by a toxic dose of topical oxygen is, however, typically cured in about two weeks by simply stopping the treatment.
Topical hyperbaric oxygen therapy calls for applying oxygen directly to an open wound. The oxygen dissolves in tissue fluids and improves the oxygen content of the intercellular fluids. Such direct application of oxygen to the wound has advantages. For example, because it is applied directly to the base of an ulcer, much lower pressures of oxygen are required for stimulating wound healing as compared to systemic oxygen therapy where diffusion is needed. Skin disorders which may be treated with topical hyperbaric oxygen include osteomyelitis, burns and scalds, necrotizing fasciitis, pyoderma gangrenosum, refractory ulcers, diabetic foot ulcers, and decubitus ulcers (bed sores). Cuts, abrasions and surgically induced wounds or incisions may also benefit from topical oxygen therapy.
The prior art teaches application of topical hyperbaric oxygen by placing the entire affected limb of a person in a sealed chamber such as one which features controlled pressure sealing and automatic regulation control. The chamber provides oxygen at hyperbaric or normobaric pressure to the entire extremity rather than only the wound site. Such hyperbaric oxygen chambers for extremities have drawbacks in that they are expensive, difficult to sterilize and have a potential for cross-infection. A suggestion for overcoming these drawbacks calls for replacing the permanent chamber with a disposable polyethylene bag. While this technique will remove the problems of sterilization, and part of the expense, it still has its disadvantages. For one, an external source of oxygen must be supplied. Even though the chamber may be quite small, pressurized oxygen, even at pressures as low as 1.04 atm, must be supplied from an external reserve. This requires a patient to be positioned near an oxygen tank during treatment. Moreover, because an entire limb is placed in a chamber or polyethylene bag, large areas of skin may be unnecessarily subjected to potentially toxic levels of oxygen. Also, the sealing mechanism of the chamber or bag may cause an undesirable tourniquet effect on the limb that is undergoing treatment.
The present invention contemplates an improved device and method for modulating the supply of concentrated hyperbaric oxygen to skin wounds. The device is disposable and therefore eliminates the risk for cross contamination. Also, it frees a patient from being confined to a pressurized source of oxygen. Hyperbaric oxygen may be supplied directly to localized areas of skin economically and conveniently without unnecessarily restricting blood flow to the treatment area. In addition, this device is capable of depleting the wound site of oxygen, which may lead to cell hypoxia. Moderately severe hypoxia has been found to promote capillary budding and proliferation. New capillaries are formed (neo-angiogenesis) in response to initial tissue hypoxia. As a result of increased blood flow, the increased oxygen tension in the tissues stimulates a complex healing process to close the wound. Thus, by increasing or decreasing (i.e., modulating) oxygen supply, one can stimulate wound healing in a most advantageous manner.